The rising obesity rate across all age groups underlines the dramatic increase in the incidence of diabetes in the United States; according to CDC, 29.1 million people or 9.3% of the population in the U.S. have diabetes with an estimated total cost of $245 billion to the healthcare system. The medical community has recognized that diabetes treatments should ideally lead to both blood glucose control and weight loss. The mission of Transira Therapeutics is to develop innovative best-in-class therapies for diabetes/obesity using our proprietary peptide and protein cross-linking chemistries. The goal of this project is to develop the chemically cross-linked (?stapled?) oxyntomodulin-Fc fusion protein as a once-weekly therapy for treatment of diabetes and obesity. In our preliminary studies, we designed a series of stapled oxyntomodulin (OXM) analogs that show a balanced subnanomolar dual GLP-1R/GCGR agonist activity along with the extended in vivo half-life. In this phase I application, we have two specific aims: (1) Preparation and biological evaluation of the stapled OXM- IgG4Fc fusion protein for higher potency and extended plasma half-life; and (2) Pre-clinical evaluation of the weight loss, glucose control, and acute metabolic effects of the stapled OXM-Fc fusion protein in DIO mice. We expect to identify one stapled OXM-Fc fusion protein with >36 hours of plasma half-life following subcutaneous (s.c.) administration in mice (comparable to dulaglutide) along with a balanced subnanomolar in vitro potency toward GLP-1R and GCGR (Aim 1), and that the stapled OXM-Fc fusion protein achieves >25% decrease in fasting glucose levels and >20% body weight reduction (greater than dulaglutide) after s.c. administration compared to placebo over 4 weeks with improved glucose metabolism (> 25% reduction in AUC for OGTT at day 28), metabolic profile and body mass composition (Aim 2). The successful conclusion of the proposed phase I studies should lay a solid foundation for IND-enabling PK and toxicology studies in the phase II period.